Vacuum tube



Oct. 25,1927.

H. E. METCALF VACUUM TUBE Filed July 25, 1924 Inventor: Herbert E. Metoalf- Patented Oct. 25, .1927.

uN rEo STATES PATENT OFFICE.

HERBERT E. ME'ICALF, on SAN EEANDR o, cALIEoRNIm'AssIGNoR TO THE MAG- NAvo'x COMPANY, E OAKLAND, cAmEormIA, A CORPORATION 0E ARIZONA.

I VACUUM TUBE. I

Application filed vI 1lvt'a3,

This invention relates to vacuum tubes of the three-electrode type for use as rectlfier s, r mplifiers, and electric wave generators. The

'objectof the invention is to improve the construction and operation of such a device, whereby it is made more sensitive to weak oscillations, and whereby a. strength and rigidity of construction may be vobtained which is greatly desirable.

In the construction of three-electrode tubes, the practice has become quite general to employ a grid between the plate and the filament, usually in the form of a wire "or plurality of wires wound in the form of a spiral, the theory being that such a grid con trols the electron stream byhaving imposed .u on it miiiute volta echan es. Sucha rid P g g g must necessarily ofier great mechanical 0bstruction to the electrons, and being' interposed-"between the filament and the plate, causes the device to have a high gridplate capacity.

In the present invention I, do not enmiloy the usual grid form for the third electrode, but make use of a novel form and arrangement which I term a control electrode.

In my invention I place the control electrode in such a position that it is not between the filament and the plate in any manner, and is therefdreentirely out of the electron stream. It is so designed, however, that the efiect of its minutest voltage changes are concentrated on the filament, and. thus fully effeet the emission of. electrons from the filament, whereby extreme .sensitiveness is obtained, and in the case of amplifying tubes extremely high amplification factors are'obtainable.

Inasmuch as the control electrode in the it is not subject to microphonic noises which are present in the type of three electrode vacuum tube wherein the grid is composed of a plurality of wires interposed between the filament and the plate. One form which my invention may assume is exemplified in the following description and illustrated-in the accompanying drawin in which 1g. 1 shows a perspective view of a vacuum. tube constructed in-accordance withmy invention, parts of the bulb being. broken away for the sake of clearness;

1924. Serial No. 727,708.

Fig. 2 shows a side elevation of the same device;

Fig. 3 shows a sectional view in plan of j the same. I

Throughout the various vfigures of the drawings I. show a sealed vessel or tube 10 containing plates A and A a filament B,

and a control electrode C. This control electrode is usually a piece of metal which has been slotted and which has had the filament. inserted in the slot. The spacing between the- 'edges of the control electrode and the filatubes of different characteristics, and with the proper width of the control electrode slot and the proper anode spacing, any desired characteristics for commercial use of such vacuum-tubes may be obtained. Y The control electrode is supported on the base of the tube by means of a post 9.

-It will be noticed that the edges of the control electrode slot do not in anyway interfere with the passage of electrons to the anode from the filament or cathode, and that the entire mechanical body of the control electrode, is in no way interposed between the filament and the anode,but controls the electron stream by electro-static field concentration on the filament as described in my co-pending application, Serial Number 695,681, filed February 28, 1924.

It has been definitely proved that superior results can be obtained by use of a control electrode as described in the present invention; higher amplification constahtsare available; mechanlcal simplicity and rugged strength have been obtained without sacrificing volume or sensitiveness; vibration which causes microphonic noises in the outvput circuit of such a device are practically sists of two separate pieces of metal placed in the proper location to receive the electron stream. These'anodes have a rib or depres+ Q I 1,646,626 sion 11. running down the entire length of employedwithout departing from the spjrit the middle of the anode which receives a of my invention as disclosed 'in the apsupporting wire 12. This rib not only serves pended claims.

for an attachment of the anode material to What I claim and desire to secure by Letg g 5 the supporting wires, but also aids greatly ters Patent is: g in stiffening such a flat surface. These sup- 1. A three-electrode vvacuum tube, comporting wires are connected together by a prising an anode, an integral, flat, sheet yoke 13, which ties the entire anode assembly metal, control electrode of a self-supporting Q I together, making it extremelystrong and character, having a substantially V-shaped 10 rugged, I slot cut therein, a filament arranged insaid In the particular form illustrated, the slot, and means for supporting the filament control electrode is in-the nature of a triin spaced relation to the edgesof the slot.

angularshaped metallic plate, and the fila- 2. A three-electrode vacuum tube compris- 35 ment is carried in a V-shaped slot formed ing an anode, a control electrode stamped 15 in this plate, being supported at its apex by from a single sheet of metal and having two means ofan arm 14 projecting out from a slots cut, therein extending from the. top

standard 15. thereof to a point near the base, mea ns at ,Other formsjof construction than those. the base of said control electrode for suphere illustrated and described will be ap-- portin the same, and a filament arranged 2 parent to thosekskilled in the art, such as in sai slots.

making the control electrode in the form of 1 a bent wire or other manners, and may be E E. METGALF. 

